Re: [PATCH v9 2/2] hung_task: Log summary line when warning budget is exhausted

On Sat, Aug 15, 2026 at 12:27:34AM +0800, Lance Yang wrote:
> 
> On Fri, Aug 14, 2026 at 09:57:18AM -0400, Aaron Tomlin wrote:
> >Once the warning budget is exhausted, hung_task_info() stops printing
> >per-task details. To provide visibility without causing additional log
> >spam, emit a single aggregate summary line at the end of each watchdog
> >scan when hung tasks are detected and the warning budget is exhausted.
> >
> >Keep per-task reports budgeted to avoid flooding dmesg or causing
> >ring buffer overflows during system-wide hangs.
> 
> Hm... not quite unconditional. hung_task_call_panic still gets through
> budget gate, so with hung_task_warnings=1 and hung_task_panic=2, first
> task can exhaust budget and second one still gets full details (right
> before panic).
> 
> I'd write changelog like this:
> 
> Once the warning budget is exhausted, hung_task_info() normally stops
> printing per-task details. When panic is triggered, full details are
> still printed so diagnostics remain available before panic.
> 
> To retain visibility without restoring per-task output after budget
> exhaustion, emit a single aggregate summary line at the end of each
> watchdog scan that detects hung tasks with an exhausted budget. This
> keeps non-panic per-task reports budgeted during system-wide hangs.

Hi Lance,

Acknowledged.

> >Suggested-by: Petr Mladek <[email protected]>
> >Suggested-by: Lance Yang <[email protected]>
> >Signed-off-by: Aaron Tomlin <[email protected]>
> >---
> > kernel/hung_task.c | 6 +++++-
> > 1 file changed, 5 insertions(+), 1 deletion(-)
> >
> >diff --git a/kernel/hung_task.c b/kernel/hung_task.c
> >index 53499fbead83..f5eb75325f3a 100644
> >--- a/kernel/hung_task.c
> >+++ b/kernel/hung_task.c
> >@@ -268,7 +268,7 @@ static void hung_task_info(struct task_struct *t, unsigned long timeout,
> > 		debug_show_blocker(t, timeout);
> > 
> > 		if (!hung_task_warnings_printed)
> >-			pr_info("Future hung task reports are suppressed, see sysctl kernel.hung_task_warnings\n");
> >+			pr_info("Future hung task reports won't print details about each process, see sysctl kernel.hung_task_warnings\n");
> 
> Same exception here... next task can hit panic threshold and print full
> details anyway (and this line can be printed while hung_task_call_panic
> is already set).
> 
> I'd make condition and message match actual behavior:
> 
> "hung_task: further per-task details suppressed until warning budget is
> reset or panic is triggered (see sysctl kernel.hung_task_warnings)\n"

Agreed.

> No need to resend just for these ... I think Andrew can fix them up when
> applying :)
> 
> Otherwise, LGTM.
> 
> Reviewed-by: Lance Yang <[email protected]>

Understood. Thank you Lance. Andrew, please let me know if otherwise.

Kind regards,
-- 
Aaron Tomlin